Evaluation has become a key tool in assessing the performance of international organizations, in fostering learning, and in demonstrating accountability. Within the United Nations (UN) system, thousands of evaluators and consultants produce hundreds of evaluation reports worth millions of dollars every year. But does evaluation really deliver on its promise of objective evidence and functional use? By unravelling the internal machinery of evaluation systems in international organizations, this book challenges the conventional understanding of evaluation as a value-free activity. Vytautas Jankauskas and Steffen Eckhard show how a seemingly neutral technocratic tool can serve as an instrument for power in global governance; they demonstrate and explain how deeply politics are entrenched in the interests of evaluation stakeholders, in the control and design of IO evaluation systems, and to a lesser extent also in the content of evaluation reports. The analysis draws on 120 research interviews with evaluators, member state representatives, and IO secretariat officials as well as on textual analysis of over 200 evaluation reports. The investigation covers 21 UN system organizations, including detailed case studies of the ILO, IMF, UNDP, UN WOMEN, IOM, UNHCR, FAO, WHO, and UNESCO. Shedding light on the (in-)effectiveness of evidence-based policymaking, the authors propose possible ways of better reconciling the observed evaluation politics with the need to gather reliable evidence that is used to improve the functioning of the United Nations. The answer to evaluation politics is not to abandon evaluation or isolate it from the stakeholders but to acknowledge surrounding political interests and design evaluation systems accordingly.